Mechanically variable complex slot



July 19, 1960 H. E. SHANKS 2,946,057 MECHANICALLY VARIABLE COMPLEX SLOTFiled June l8, 1958 United rates Hughes Aircraft Company, Culver City,Calif., a corporation of Delaware Filed June 18, 1958, Ser. No. 742,805

s Claims. 01. 343-768) The present invention relates to a variableconductance waveguide slot, and more particularly to-a mechanicallyvariable complex slot.

In general, slots disposed along the centerline of a rectangularwaveguide do not radiate. because the current distribution within thewaveguide is such that there is zero value of current in the area of theslots. Slots may be cut ofi the centerline in the broad wall of awaveguide which will radiate, and those slots which are angularlydisposed radiate with a phase difference with respect to those slotsparallel to the centerline. Such angularly disposed slots are, for thepurposes of this application, termed complex slots.

Also, as has been previously taught, slots along the centerline of thebroad wall of a waveguide may be made to radiate by inserting a deviceresulting in asymmetrical disturbance of the current distribution withinthe waveguide. This latter teaching is discussed in detail in anapplication for Letters Patent, Serial No. 740,160, filed June 5, 1958,for Variable Conductance Waveguide Slot by Howard E. Shanks and BernardJ. Maxum.

The previous methods and structure for making centerline waveguide slotsradiate have principally provided for variation of the radiation inamplitude with possible phase reversal, if desired. The amplitude of theradiation from these slots depends on the intercepted current densityand the value of the component of the current which is transverse to theslot. The phase reversal is dependent upon the direction in which thecurrent component crosses the slot, and this latter, in the previouslydevised methods, has been limited to one or the other transversedirection.

The present invention, in brief,-comprises a section of rectangularwaveguide having at least one centerline slot and two variable irisesdisposed transversely within the waveguide, one at either end of theslot. With such arrangement it is possible to disturb the currentdistribution within the waveguide so that current crosses in onedirection at one end portion of the slot and in the other direction atthe other end portion. Thus, such centerline slot resembles the abovereferenced complex slot, but the phase is variable from zero to 360degrees.

It is therefore an object of the device of the present invention toprovide a variable complex slot.

Another object is to'provide a variable conductance slot which may bevaried as to phase and amplitude of radiation.

Still another object is to provide a variable conductance slot whereinradiation from the end portions is separately and selectively variable.

A further object is to provide a centerline wavegiude slot withasymmetrical means disposed within the waveguide for variablycontrolling the phase and amplitude of radiation from the slot.

Other objects and advantages of the invention will be apparent from thefollowing description considered together with the accompanying drawing,in which:

Fig. 1 is a perspective view, partly in section, of the device of theinvention; and

atent ice Fig. 2 is a schematic plan view illustrating several currentpatterns for difieren-t positions of the irisesof Fig. 1.

Referring to Fig. 1 in detail, there is. shown a rectangular waveguide11 for propagating electromagnetic energy from a source (not shown)which maybe coupled to input port 12. Resonant slots 13 are provided ina broad wall of the waveguide 11 extending along the longitudinalcenterline thereof. When the electromagnetic energy propagated throughthe waveguide 11 is in the dominant mode, TE1o, the current distributionin the area of the slots has a zero value and therefore there is noradiation from the slots. V

To make the slots 13 radiate, the same structure gen{ erally indicatedat 14 is provided with respect to each slot and only one will bedescribed in detail with similar reference numeralsbeing applied in eachinstance. A first metallic iris 16 having induotiveside plates 17 and 18connected by an impedance matching capacitive plate 19 at the lowerportions thereof is disposed transversely within the waveguide 11.Aligned and oppositely disposed sidewall slots 21 and 22 extendtransversely between the broad walls in a plane which intersects slot 13at one end to slidably receive extensions of side plates 17 and 18. Asecond similar metallic iris 26 is disposed at the other end of the slot13 and comprises inductive side plates 27 and 28 and impedance matchingcapacitive plate (not shown) with the side plates engaging sidewallslots 31 and 32 of waveguide 11. Such sidewall slots 21, 22 and 31, 32normally do not radiate because current flow in waveguide 11 at thesidewalls is parallel to these slots.

As an example of a manner of making the lateral position of irises 16and 26 adjustable within slot 13, two matching side elements 36 and 31are externally mounted in spaced-apart relation at either side of slot13 on waveguide 11 parallel to the irises and engage the waveguide byapertures 38 and 39, respective1y. To provide'a rigid framework, endbrackets 41 and 42 are suitably secured to the respective ends of sideelements 36 and 37,'as by screws 43. For convenienceofinstallationand;fabrica'- tion, the side elements 36 and 37 may be dividedlongitudinally and secured together, as by screws 44; The end brackets41 and 42 each have apertures 46 and 47 toreceive conventionalmicrometer type rotary-to-linear motion translators 48, 49,respectively, which engage an extension of one side plateof each iris 16and 2-6, as by pins 51. Vernier scales 52.are provided for eachtranslator 48, 49 to permit fine adjustment thereof and calibration ofthe characteristics of the slot radiation. Thus, by rotating knobs 53and 54, respectively, the amount of each inductive side plate within thewaveguide 11 is adjustable. i

Considering now the operation of the variable conductance slot 13, whenconstructed in accordance'with the foregoing, and, as an aid in theunderstanding thereof, reference is made to the schematic plan View ofFig. 2-. With the irises 16 and 26 symmetrically positioned by suitablemanipulation of translators 48 and 49 within the waveguide 11 .withrespect to the slot .13, current flows equally in the inductive sideplates 17, 18 and 27, 280i each his to provide equal values of inducedmagnetic field on each side of the waveguide. Therefore, the currentdistribution, as disturbed by irises 16 and 26 within the waveguide 11,is still symmetrical and no radiation results, as indicated by thecurrent distribution pattern indicated by curved lines 61 of Fig.2. I j

When the irises 16 and 26 are respectively displaced-in the samedirection toward one side wall of waveguide 11 to dispose a greaterportion of one inductive side plate of each iris within waveguide 11 anasymmetry is introduced in the current distribution and more currentflows in side plates 17 and 27 than in the other side plates 18 and 28.Thus, there is a, greater value of induced magnetic field on one side ofthe waveguide 11 and the current distribution, as illustrated in.current pattern 62, is forced away from the side having the greatervalue of induced magnetic field. The result of the foregoing is asubstantial value of current component transverse to the slot 13 andtherefore the slot radiates.

With one iris 16 moved transversely in one direction and the other iris26 moved oppositely, a current distribution pattern 63 results withcomponents of current transverse to the slot in one direction at one endthereof and in the opposite direction at the otherjend. When theposition of the irises 16 and 26 is reversed with respect to that justdescribed, the current distribution is altered in the oppositedirection, as seen in current pattern 64. I,

From the foregoing it is apparent that by suitable adjustments of thetranslators 48 and 49, radiation of variable amplitude and phase isattainable from the slot 13. A single variable conductance complex slotin a waveguide is useful as a variable coupler or as a switch. Aplurality of such slots suitably spaced apart along the centerline of awaveguide, as indicated by the two slots shown in Fig. 1, isparticularly useful as an antenna array for obtaining those complexpatterns of radiation which are dependent upon the phase of theindividual radiating elements as well as upon the amplitude. Also, suchwaveguide slot arrangement may readily be remotely controlled as byselsyns which, in turn, are easily adapted to programming by devicessuch as computers for adjustment of the slots individually.

In the foregoing, the description and illustration of the structure ofthe invention has been set forth in particularity with respect toresonant slots along the longitudinal centerline of the broad wall ofthe waveguide. It is to be noted, however, that the applicableprinciples are not limited to such centerline resonant slots, but may beequally applied with respect to resonant slots having any positionthrough a broad wall of the waveguide. For an array of resonant slotsoff-thecenter line a complex type of calibration procedure is involved,which makes it desirable to use the described centerline resonant slots.

While the salient'features of the present invention have been describedin detail with respect to a particular embodiment, it will be-readilyapparent that numerous modifications may be made within the spirit andscope of the invention, and it is therefore not desire'd' to limit theinvention 'to the exact details shown except insofar as they may bedefined in the following claims.

What is claimed is:

1. A variable conductance waveguide slot coupler comprising arectangular waveguide having a resonant slot in a broad wall thereof,first and second iris means mounted within said waveguide andrespectively disposed at opposite ends of said slot, and means coupledto said first and second iris means for individually varying thepositions thereof to alter current distribution of energy propagatedthrough said waveguideand control radiation from said slot.

2. A variable conductance waveguideslot coupler comprising a rectangularWaveguide having a resonant slot through one broad wall of saidwaveguide along the longitudinal center line thereof, first iris meansdisposed within said waveguide at one end of said slot, second irismeans disposed within said waveguide at the other end of said slot, andmeans for individually varying the position of said first and secondiris means to alter current distribution of energy propagated throughsaid waveguide and cause said slot to radiate.

3. A variable conductance waveguide slot coupler comprising arectangular waveguide, a resonant slot through one broad wall of saidwaveguide along the longitudinal centerline thereof, first and secondiris means mounted transversely within said waveguide and respectivelydisposed at opposite ends of said slot, and means disposed externally ofsaid waveguide and coupled to said first and second iris means forindividually varying the position of such iris means to alter currentdistribution of energy propagated through said waveguide and controlradiation of energy from said slot in amplitude and phase.

4. A variable conductance waveguide slot coupler comprising arectangular waveguide, a resonant slot through one broad wall of saidwaveguide along the longitudinal centerline thereof, first and secondiris means mounted transversely within said waveguide and respectivelydisposed at opposite ends of said slot, each of said iris meansincluding inductive side elements slidably engaging side wall openingsof said waveguide, and means coupled to at least one side element ofeach of said irises for individually varying the inductive effect ofsaid side elements to alter current distribution of energy propagatedthrough said waveguide and control radiation from said slot in amplitudeand phase.

5. A variable conductance waveguide slot coupler comprising arectangular waveguide having a resonant slot through one broad wallthereof, first and second iris means slidably mounted transverselywithin said waveguide between substantially nonradiating side wallapertures and respectively disposed at opposite ends of said slot, eachof said iris means including two spaced-apart inductive side plates withan impedancematching capacitive plate disposed therebetween, and meansmechanical ly coupled to each of said iris means for individuallycontrolling the transverse position thereof to alter currentdistribution of energy propagated through said waveguide and controlradiation from said slot in amplitude and phase.

6. A variable conductance waveguide slot coupler comprising arectangular waveguide having a resonant slot through one broad wallthereof, first and second iris means slidably mounted Within saidwaveguide between substantially nonradiating side wall apertures andrespectively disposed at opposite ends of said slot, each of said irismeans including two spaced-apart inductive side plates having portionsextended through said side wall apertures with an impedance matchingcapacitive plate disposed therebetween, a frame mounted on saidwaveguide about said slot, and first and second means supported by saidframe and respectively coupled to said iris means for establishing thetransverse positions thereof to alter current distribution of energypropagated through said waveguide and control radiation from said slotin amplitude and phase.

7. A multiphase and multipattern antenna comprising a section ofrectangular waveguide having a plurality of spaced-apart resonant slotsthrough a broad wall along the longitudinal center line thereof, aplurality of adjustable irises transversely mounted within saidwaveguide and respectively disposed at opposite ends of each of saidslots, and means individually coupled to each of said irises forseparately adjusting the transverse positions thereof and controllingthe amplitude and phase of radiation from said slots by asymmetricaldisturbance of current distribution in thearea of each slot asestablished by energy propagated through said waveguide.

8. A multiphase and multipattern antenna comprising a section ofrectangular waveguide having a plurality of spaced-apart resonant slotsthrough a broad wall aiong the longitudinal centerline thereof, aplurality of adjustable irises transversely mounted within saidwaveguide and slidably engaging substantially nonradiating side wallapertures, one of said irises disposed at each end of each www energypropagated through said waveguide and provide amplitude and phasecontrol of radiation from said slots individually.

References Cited in the file of this patent UNITED STATES PATENTS ClappNov. 6, 1951 Ajioka et a1 Dec. 31, 1957

